As long as they don't try to do something stupid, like make it the "Battle of Gettysburg Casino" or something. Keep it respectful, keep it separate from the battlefield, and for cryin out loud RESEARCH the ground you're planning on building it on! Don't throw it up on top of a battlefield, or skirmish site. Have some respect. But this is America, and our economy sucks, so building this thing will help provide jobs, it'll get tourists into the Gettysburg area, and if we start telling businesses where they can/can't build, then we might as well start calling ourselves the Soviet States of America. Besides....the eastern states have seen so much war during the history of this country (even before we were a country), there's probably not a whole heckuvalotta area that isn't going to be historical or sacred in some way.
Now, if they go and try to make it a tourist attraction and make extra bucks off the battlefield, like that guy did years back by making a profit off of Titanic memorabilia, then I'll have an issue with it. And so will the countless ghosts that still roam the area....